This invention relates to a finger plate used in stringed instruments, such as guitars, mandolins and ukuleles, having frets which are located corresponding to musical intervals.
As shown in FIG. 5, a prior finger plate for a stringed instrument, for instance, a finger plate for a guitar 100 is constituted by a finger plate main body 108, a nut (or an upper nut) 107 which holds one end of each of six strings 101-106, and a plurality of frets 111 each of which is provided on the finger plate main body 108 with a specific distance from the nut 107 and in parallel with the nut 107. Note that a zero fret 110 is formed on the inside surface of the nut 107.
The above specific distance is, based on the position where each of the frets 111 is formed. The positions are between the surface of the nut 107 and a saddle (a lower nut), not shown in the figures which holds the other end of each of the plural strings 101-106, and are determined by calculating temperament of natural scale on the finger plate at the zero fret 110.
In regard to this constitution, Japanese Utility Model Registration No. 3,012,510 discloses a stringed instrument which has a plurality of frets which constitute parts of radii extending from the same center point, with especially one fret located in a center of the finger plate being perpendicular to a longitudinal axis of the finger plate. Japanese Unexamined Patent Publication No. 8-83064 discloses a guitar for which metallic parts of the frets are slanted so that the frets are not in parallel to one another.
However, as shown in FIG. 6, distances L1'-L6' between frets 111 in each of strings 101-106 become longer from a center toward both outer sides, and angles .alpha.1-.alpha.6 between each of strings 101-106 and each of the frets 111 become larger from the center toward both outer sides, so that the strings 103 and 104 located in the center and the strings 101 and 106 located at both outer sides are significantly different in distance from the zero fret 110. As a result, though the frets 111 are located in correct positions calculated by the original temperament, there may be a bad condition such that it is difficult to obtain strict musical intervals.
Furthermore, when the strings cross the frets obliquely, one side of the string has obtuse angles with the frets and the other side of it has acute angles with the frets. As a result, the one side is free against vibration of the string, but the other side is not free against vibration of the string is arisen, which is a bad condition preventing the string from being vibrated accurately. Thus, in all of the above devices, because the frets and the strings do not cross each other perpendicularly, they have the above bad conditions.
Moreover, the above bad conditions are especially apparent when plural strings are pressed down in order to play a chord. In other words, because each pitch gap of the strings is different from one another in the strings and the positions pressed down, so that a discord different from the original chord constitution is added to the sound condition of the chord. As a result, there is a problem in that it is difficult to obtain an exact musical interval and a good balance.
Furthermore, in prior instruments such that the frets are arranged in parallel with one another, because grooves in which the frets are mounted are formed in parallel with one another, they would have a disadvantageous constitution with respect to the resistance to tension of the strings. Namely, in the condition that drying of wood itself progresses, the grooves formed in parallel with one another are directly affected by the tension of the strings because each of the grooves is formed with a size with allowance in the width and the depth for a base portion of the fret. As a result, warping or twisting of a neck or the finger plate itself may occur disadvantageously.